Bourbon Distillation: Everything You Need To Know

How bourbon is actually made.

Bourbon Distillation

What is bourbon distillation?

Bourbon distillation is the process in which a fermented corn and grain mash liquid is heated to create a vapor, and then condensed back into a liquid again. The liquid is typically distilled twice.

In the first round, most distillers put bourbon through column stills. The second round typically distills it through copper pot stills.

These distillation steps boost the alcohol content and remove impurities.

Typically the more that bourbon is distilled, the purer, smoother, and lighter the final blend is. Oak barrel aging may give a slight heaviness to the bourbon.

Bourbon Distillation Rounds: The Science

Discover the science behind bourbon distillation!

First distillation round

Find out how fermented mash is transformed into high-proof alcohol through a column still, and what happens to the by-products of the process.

  • Fermented mash is piped into the column still and heated from the lower end
  • Mash and water settle at the bottom, while gaseous alcohol flows upwards
  • Rising alcohol vapor is condensed in the first tail box, resulting in a grungy blend called low wine
  • Distilled alcohol is extracted at the top of the column still, while water and mash accumulate at the bottom as stillage
  • Stillage is processed into animal feed and sour mash is reintroduced into the fermentation process

Did you know? Taller columns stills produce a higher alcohol content than smaller columns.

Second distillation round

The distilled alcohol undergoes a second round of distillation in a copper pot still to improve its taste.

  • Alcohol steam passes through a copper pot, called a doubler, for catalytic conversion to improve taste
  • Distillate from the first round is re-distilled to remove more impurities and water
  • After the second round of distillation, the vapor is liquefied again in a condenser
  • Distilled alcohol is strong at 130 proof and colorless, termed as high wine or white dog
  • Alcohol is diluted and tested for flavors, concentration, and purity standards before being filled in charred new oak barrels

Triple-distilled bourbon

Most bourbon whiskey is distilled twice. Triple-distilled bourbons like Woodford Reserve go through a third distillation round in a copper pot.

Triple-distilled bourbon is a more expensive process than double-distillation.

Scotch, Irish whiskey, and bourbon can be triple-distilled. Crown Royal Canadian whisky is also triple-distilled.

It’s debatable, but triple-distilled whiskies are believed to be ‘lighter’.

Related: Bourbon vs Whiskey vs Scotch: What’s The Difference?

Bourbon Column Still


Bourbon distillation occurs in a still.

Column stills are often used for bourbon and other American whiskies.

There are two main types of stills, the column still and the copper pot still.

Bourbon Copper Pot Still


Copper pot stills are typically used to triple-distilled bourbon.

Their size, shape, and material can affect the flavor of bourbon. Copper can enhance the distillate profile and preserve the original flavors.

With a pot still, it’s possible to remove the heads and tails of the distillate to extract the best alcohol, whereas in column stills, everything is either vapor or collects at the bottom of the still.

Bourbon Distillation Proof

Bourbon cannot be distilled to more than 160 proof initially. And it must go into the barrel at no more than 125 proof.

  • 160 proof, or 80% alcohol-by-volume (ABV), is as high as bourbon can reach off of the still.
  • Bourbon must go into the barrel at no higher than 125 proof. Distillers add water to “proof it down”.
  • Bourbon must not be lower than 80 proof at that time of bottling.

As it ages, bourbon increases in proof. So distilleries may choose to barrel at a lower proof.

The History of Bourbon Distilling

Bourbon isn’t just a spirit; it’s a piece of American history. The legends surrounding its creation add to its allure.

Kentucky Origins

Scots, Scots-Irish, and other settlers brought distilling to present-day Kentucky in the late 18th century. They began farming the area and using their skills to create a distinct form of whiskey.

While there are conflicting stories about the invention of bourbon, it’s clear that the process of aging whiskey in charred oak casks originated in Kentucky.


Prohibition devastated the bourbon industry, with all distilleries forced to shut down.

Some were granted permits to bottle existing stocks of medicinal whiskey, and a few were allowed to resume production when the stocks ran out.

The Bourbon Name

The origin of the name “bourbon” is debated.

Some argue that the name comes from the geographic region of Old Bourbon, in Eastern Kentucky.

While some others propose that bourbon whiskey was named after Bourbon Street in New Orleans.

When did bourbon distillation begin in the United States?

Some believe that the Reverend Elijah Craig (a Baptist minister) was the first to distill bourbon whiskey in the U.S. in 1789.

His bourbon was distilled in Bourbon county Kentucky. And the barrels were stamped as “Bourbon County Whiskey”.

Can I distill bourbon at home?

Home distillation is very illegal in the United States.

According to the U.S. tax code, individuals are prohibited from distilling alcohol for personal consumption. Distilleries need federal, state, and local permits to do so.

Fines & Jail Time

Distilling spirits at home can expose you to Federal charges including 5 years in prison and a fine of up to $10,000 for each offense.

Here are other title 26 of the United States Code, section 5601 criminal activities that can land you in hot water with the U.S. Department of the Treasury:

  • 5601(a)(1) – Possession of an unregistered still.
  • 5601(a)(2) – Engaging in business as a distiller without filing an application and receiving notice of registration.
  • 5601(a)(6) – Distilling on a prohibited premises. (Under 26 U.S.C. 5178(a)(1)(B), a distilled spirits plant may not be located in a residence or in sheds, yards, or enclosures connected to a residence.)
  • 5601(a)(7) – Unlawful production or use of material fit for production of distilled spirits.
  • 5601(a)(8) – Unlawful production of distilled spirits.
  • 5601(a)(11) – Purchase, receipt, and/or processing of distilled spirits when the person who does so knows or has reasonable grounds to believe that Federal excise tax has not been paid on the spirits.
  • 5601(a)(12) – Removal or concealment of distilled spirits on which tax has not been paid.

Alos, don’t even think about trying to avoid alcohol tax.

Under 26 U.S.C. 7201, any person who willfully attempts to evade or defeat any Internal Revenue Code alcohol tax is committing a felony and will be fined up to $100,000, imprisoned for up to 5 years, or both, plus the cost of prosecution.

By law, you cannot distill bourbon at home.

Bourbon Distillation Process

Here’s how bourbon is made:

Determine the Mash Bill

The master distiller first determines the recipe (or mash bill) of different grains to use for the bourbon’s creation.

The American Bourbon Association requires that bourbon sold in the United States is distilled from a mixture of grains (or mash) that must be comprised of at least 51 percent corn.

The grain is ground and mixed with water to create a sour mash, which is then fermented with yeast to produce a clear spirit known as “white dog.”

The white dog is then placed in charred new oak barrels, which are made from American white oak and lend the bourbon its distinct flavor and color.

Combine the Base Ingredients

To make a fermentable base, distillers will mix grains—corn, rye, and barley malt—with water and yeast.

They then heat and stir the mixture (sometimes called “bourbon mash”) to ensure it’s well combined and ready to ferment.


For the fermentation process, bourbon makers store their base mixture in a vat for a specified amount of time—from one to two weeks—to fully ferment the mixture.

During this step, the compounds begin to break down and produce a simple, natural alcohol called ethanol or ethyl alcohol. Yeast and sour mash are added to the mixture at this point.

Sour mash is the leftover mash from a previous distillation, which reduces the mash’s pH to prevent bacteria growth.

Strain the Mixture

Once fermentation is complete, distillers strain off the liquid from the fermented solids.

They’ll discard the solids and use the liquid (ethanol) to make the bourbon.


Distillation is a process that purifies a liquid by heating and vaporizing it, then collecting the vapor as it condenses into a liquid.

The resulting liquid (distillate) is considered purer (since it leaves behind many impurities when it evaporates) and more alcoholic.

A majority of bourbon is put through the distilling process twice. The first round involves distillation in a beer still.

The second round involves distillation in heated copper pot stills, referred to as doublers or thumpers.

These rounds serve to boost the alcohol content and remove impurities.

Aging and Barreling

Once the bourbon reaches between 80 and 125 proof, distillers must age it in a new charred oak barrel for at least two years before it can be called straight bourbon.

Changes to the spirit occur due to evaporation and chemical processes such as oxidation. The longer the bourbon is aged, the richer and more complex its flavor becomes.

(The aging process is shorter than that of Scotch whiskey from Scotland, which must age for three years.).

The charred layers of oak help caramelize the sugars, contributing to the spirit’s distinct flavor and color.

Depending upon how a distiller wants the barrel to affect their bourbon, they can choose the degree to which the oak barrel or oak container is charred.


Before bottling, distillers may chill-filter the bourbon to remove any long-chain protein molecules and impurities that may cause the spirit to become hazy or cloudy when stored at low temperatures.

To ensure the proper alcohol content, distillers test and dilute their product with filtered water before or after aging (sometimes both).

Once the spirit is bottled, it stops aging.

Water Transport

Kentucky bourbon developed a superior taste because it was shipped in barrels using water transport wherever possible.

Barrels that make a waterborne journey have been found to be richer and more complex than other samples.

Bourbon Corn Percentage

Bourbon whiskey is an alcoholic beverage made from the fermented mash of cereal grains, the majority of which is corn.

Technically, bourbon must be made with at least 51% fermented corn mash. The other 49% is often a mixture of grains like rye, wheat, or malted barley.

Bourbon can be made from 100% corn. By law there is no maximum limit.

Visit a bourbon distillery

A great way to develop a bourbon whiskey palate, is to visit distilleries and booking guided tastings.

This allows for an understanding of basic flavor notes and what makes them prominent, while also providing a chance to experience the surroundings of the distillery, such as the scents of the warehouse and the trees and bushes nearby.

The more distilleries you visit, the more sensory memories you’ll have and the better frame of reference for future tastings.

By building these sensory memories, the nuances of different bourbons will become more apparent and enjoyable.

Popular bourbon brands

Let’s talk about bourbon brands that offer guided distillery tours.

  • Jim Beam: This classic Kentucky bourbon is the world’s best-selling bourbon. Sometimes, the best stuff is the most affordable.
  • Maker’s Mark: Another Kentucky bourbon, Maker’s Mark is known for its distinctive red wax seal and its smooth, balanced flavor profile.
  • Bulleit BourbonYou’ll also taste some sweetness from the corn and a hint of smokiness from the charred oak barrels.
  • Wild TurkeyThis Kentucky bourbon is a dependable bourbon that is bottled at 101 proof with a slightly hotter, spicier edge than other comparable whiskeys.
  • Knob Creek: Knob Creek is made at Jim Beam’s distillery and offers a behind the scenes tour. It’s has a nutty, rich caramel and brown sugar flavor.
  • Evan Williams: A great cheap cocktail bourbon that is stronger at 86 proof with other good expressions to try besides the classic Black Label.
  • Four Roses: An excellent budget bourbon that is great in cocktails and sipping on its own. It is one of the best bourbons you can find for the price, and the Four Roses Small Batch is also tasty and more moderately priced.

Related: 14 Best Bourbon Mixers 

Bourbon flavor profile

What does bourbon taste like exactly?

Bourbon has a flavor profile all its own.

So, what makes bourbon taste the way it does?

  • Bourbon tasting involves considering the nose, flavor, and finish on the palate.
  • The tasting notes in bourbon come from factors like yeast strain and aging in charred oak barrels.
  • There are 9 common tasting notes found in bourbon.

Tasting notes in bourbon come from various sources like the yeast strain used, mash bill, and aging process in charred oak barrels, which contribute 60% of the flavor.

Several facets explain bourbon’s unique flavor. The nine common tasting notes in bourbon include:

  • vanilla
  • wood and nuts
  • fruit
  • sweets
  • baking spices
  • floral
  • herbaceous
  • earthy
  • smoky notes

Bourbon Cocktail Recipes

All this reading got you thirsty? Sip on these bourbon cocktails!

Bourbon Distillation FAQs

What does triple-distilled mean?

Triple-distilled bourbon must be distilled three times. It’s more expensive than continuous or double-distillation. Bourbon, Scotch, and Irish whiskey, can be triple-distilled.

Why is bourbon made on a single column still in Kentucky?

Bourbon is made on a single column still in Kentucky because the intent of distillation is different from that of grain whiskey in Scotland, Ireland, and Canada. Bourbon is meant to have character and flavor, unlike grain whiskey that removes as much character as possible.

What is sour mash?

Sour mash is previously fermented mash that is used to kickstart the fermentation of a new batch of mash. ‘Set back’ is undistilled residue remaining from a distillation. Sour mash is this acidic set back.

Can you drink 25 year old bourbon?

For health and safety, it is not advised to drink bourbon or other liquors that are older than 25 years. Temperature and humidity changes can also cause deterioration of the flavor and aromas.

Does bourbon go bad?

Once a bottle of bourbon is opened, it’s shelf life is about 1-2 years. Unopened, bourbon can be stored for up to 25 years. Although it may start to lose some of it’s taste.

Does bourbon have to be made in Kentucky?

Bourbon can be made anywhere in America. Kentucky Straight Whiskey must be made in Kentucky.

How long is bourbon aged?

Bourbon is typically aged at least wo years. Most brands are aged at least four years or longer. The different flavor profiles come from how the barrels are affected by temperature. There is not usually temperature regulation in bourbon aging warehouses.

Can you use a bourbon barrel more than once?

By law, in America, a bourbon barrel can only be used once to age bourbon. A bourbon barrel spends 2+ years imparting rich flavor and color to the bourbon aging inside it.

What is the oldest bourbon distillery in America?

Buffalo Trace is the oldest bourbon distillery in the United States. During Prohibition the distillery was operational and made whiskey for ‘medicinal purposes’.

Why is bourbon aged in new barrels?

Used barrels can cause batch inconsistencies which may dilute flavoring elements from the casks.

When bourbon barrels are charred, it allows the whiskey to soak up more flavors. The carbon ash smooths the taste and takes that edge off the bourbon.

What does bourbon taste like?

Bourbon is sweeter and smoother than whiskey because it is made from at least 51% corn. Corn is naturally sweet.

What is bourbon?

Bourbon is an American whiskey. Distillers can only label a whiskey as bourbon when its mash bill is made with at least 51 percent corn and aged in oak barrels. Additional rules regulate the alcohol proof, time spent aging, bottling, labeling, mixing and more.

Bourbon whiskey can only be made anywhere in America. But most bourbon is distilled in Kentucky, which is considered its birthplace.

Written by Gina Elizabeth

Gina Elizabeth is an investment analyst and blogger. She sometimes eats pretty good, other times not. Hey, you gotta live, you know?